Kotarou's cousin, Tatsuki, developed postcognitive abilities during his childhood, which only manifested when he touched Kotarou. Initially, Tatsuki despised his powers, causing him to be distant and unfriendly towards his cousin when Kotarou first moved in. However, as the series progresses, he starts to develop affectionate feelings for Kotarou and finds it difficult to blame him for his own powers. This internal conflict leads to significant emotional turmoil and confusion.
After the death of his grandfather, Tatsuki experiences a psychotic episode and subsequently gains additional powers beyond postcognition, likely a form of psychokinesis. He attempts to kill Kazuma twice—once using his new abilities and another time by strangulation, both incidents occurring in Volume 7—but is thwarted by Kotarou. Following these events, Tatsuki seems to regain some semblance of sanity.
Tatsuki harbors a strong dislike for the child Akira and has an aversion to hospitals.
